Strain Cad16T was previously shown to fix a major fraction of the bulk CO2 under both light and dark conditions and was suggested to be involved in Fe(II) driven aerobic metabolism in the lake Cadagno chemocline. However evidence on genomic and proteomic level was only fragmentary . In order to understand the biological functions expressed under phototrophic and chemotrophic growth conditions of str. Cad16T an in situ experiment conceived. It included cultures of str. Cad16T incubated in dialysis bags for three months while physiochemical conditions were monitored longitudinally. Upon sampling, physiological differences of str. Cad16T were compared utilizing quantitative proteomics in combination with CO2-uptake measurements.